Laser oscillator

Patent Granted To extend the temperature range for a stable operation without mode hopping and obtain a stable laser oscillation, a laser oscillator is provided. The laser oscillator includes: an optical circulator in which light incident on a first port is exited from the second port, light incident on the second port is exited from a third port, and light incident on a fourth port is exited from the first port; a first optical amplification fiber that amplifies the light exited from the third port because of being excited by an exciting light and injects the same into the first port; a reflective optical filter that reflects light with a predetermined wavelength among the light exited from the second port and injects the same into the second port again; and an pump light source that generates an exciting light to excite the first optical amplification fiber.